Typically, transmission cable jacket formulations comprise a thermoplastic material that is mixed, melted and extruded about a core carrier medium. Such jacket materials can insulate single or multiple filament conductors or can be used as an outer most jacket to bind and protect a core of isolated conductors. The core carrier medium is usually electrically or optically conductive.
Insulated or jacketed transmission cables are commonly used within commercial and residential buildings for distribution of power, for communication and for electronic control systems. Depending on the environment and the application, insulated or jacketed transmission cables must pass varying performance standards designed to enhance fire safety.
Generally, electrical or optical cabling installed in buildings and dwellings must pass tests to insure that standards are met for flame spread, smoke generation and other byproducts that are generated during a fire. Previous jacket compositions designed to address the problems of flame spread and smoke generation in building fires comprised primarily thermoplastic formulations relying heavily on halogenated materials such as fluoropolymers or polyvinyl chloride (PVC). Although many of these formulations have passed the appropriate flame tests required for their installation, certain undesirable characteristics still remain.
Jacket formulations incorporating halogenated materials inevitably produce corrosive products during a fire. Formulations making use of fluoropolymers or polyvinyl chloride produce unacceptable amounts of hydrofluoric and hydrochloric acid under these conditions. Such compounds are potentially dangerous, and may damage sensitive and expensive electronic equipment because of their corrosive nature.
Some jacket formulations, such as the Lindsay & Williams Megalon S300, have incorporated nonhalogenated materials in an effort to solve these problems. However, these compositions exhibit inferior mechanical qualities, are difficult to extrude and hence unduly expensive to manufacture.
What is needed, then, is a transmission cable jacket material that offers both the mechanical advantages and the fire resistance performance of halogenated formulations while eliminating the corrosive products these formulations release during a fire.
Accordingly, it is one of the objects of this invention to provide a transmission cable jacket material that produces noncorrosive flame byproducts.
It is another object of this invention to provide a transmission cable jacket material that produces nontoxic flame byproducts.
It is yet another object of this invention to provide a transmission cable jacket material that exhibits low flame spread characteristics.
It is still another object of this invention to provide a transmission cable jacket material that exhibits low smoke production during a fire.
It is a further object of this invention to provide a transmission cable jacket material that exhibits improved mechanical performance.
It a still further object of this invention to provide a transmission cable jacket material exhibiting improved manufacturing capability.
Additional objects will become apparent from the detailed description and claims that follow.